1. Field of the Invention
The present invention relates to a film formation technique, and particularly relates to a film formation method and device, in which the formation of films on the backside of a wafer can be controlled.
2. Description of the Prior Art
Heretofore, a film formation method and device, in which Ti, TiN and W films are sequentially formed on the surface of a wafer, have been developed. For example, the following prior arts are known.
FIG. 1A diagrammatically shows an example of the prior-art film formation mechanism, and FIG. 1B shows another example thereof.
The prior art shown in FIG. 1A is disclosed in the Japanese Patent Application Laid-open No. 29241/1994. After a polysilicon film 33 is formed on an interlayer insulating film 31, a Ti film and a TiN film 35 are sequentially sputtered. In this case, the peripheral part of a wafer is supported with a clamp. After annealing, a blanket tungsten film 38 is formed. Since the blanket tungsten film 38 is formed on the polysilicon film 33, the peeling of the blanket tungsten film 38 can be prevented: otherwise, the blanket tungsten film 38 would peel off because the blanket tungsten film 38 has a bad adhesion to the interlayer insulating film 31. A titanium silicide film 37 is formed by reaction of the Ti film and the polysilicon film 33. Number 30 refers to a silicon wafer.
The prior art shown in FIG. 1B is disclosed in the Japanese Patent Application Laid-open No. 32563/1992. Both the TiN film having a large tendency to peeling and the Ti film 43 having a small tendency to peeling are formed by varying sputtering gas in a chamber 41. Particles are thus decreased in the chamber 41. Number 42 denotes a substrate holder, 44 denotes a target, 45 denotes a shutter sheet, 48 denotes a high frequency power source, 49 denotes a gas introduction system, 50 denotes an argon gas bomb, 52 denotes a nitrogen gas bomb, and 54 denotes a substrate.
The first problem with the prior art is that the effective area is reduced because the peripheral part is supported with the clamp.
The second problem is that when the TiN film and the Ti film are formed in the same film formation device, it cannot be assured that the Ti film is completely covered with the TiN film, and no margin is allowed. This is because the formation of the film on the sides and backside of the wafer cannot be controlled.
After forming the TiN/Ti films, the tungsten (W) film is formed. In this case, if the Ti film is incompletely covered with the TiN film, the W film reacts and peels. In the prior art, to avoid the peeling, when forming the Ti and TiN films, the chamber is fixed, and when forming the Ti film, the chamber is clamped, thereby preventing the Ti film from reaching the backside of the wafer. Therefore, the efficiency of maintenance is decreased for the reasons: (1) reduction of the film formation effective area; and (2) fixing of the film formation chamber.